Nylon 11 is a commercial polymer with excellent piezoelectrical and mechanical properties, and is used in a large range of industrial fields from automotive to offshore applications (see, Tianxi Liu et al., “Preparation and characterization of nylon 11/organoclay nanocomposites,” Polymer 44, pp. 3529-3535 (2003)). Nylon 11 may be used for the “ball” portion of a shuttlecock (a high-drag projectile with an open conical shape and a rounded “ball” head) in the game of badminton because of its properties such as impact strength, low melt index, and water resistance properties (see, Qin Zhang et al., “Crystal morphology and crystallization kinetics of polyamide-11/clay nanocomposites,” Polymer International 53, pp. 1941-1949 (2004)). In comparison to shuttlecocks made out of feathers of goose or duck, those made out of synthetic nylon 11 are cheaper and more durable.
However, badminton players consider the performance of shuttlecocks made out of synthetic nylon 11 to be poorer than the performance of shuttlecocks with their “ball” portion made out of feathers. In particular, a shuttlecock “ball” made out of nylon 11 may feel too soft. Its flexural modulus is around 400-500 mPa (millipascals), which is much lower than that of a feather shuttlecock. As a result, such nylon 11 materials do not enable the shuttlecock “ball” to restore its shape quickly enough. This causes prolonged wobbling and a decrease in flight distance as compared to shuttlecocks made out of feathers. On the other hand, feather shuttlecocks, due to their rigidity, restore almost instantaneously the aerodynamic shape of the shuttlecock, thereby enabling a nearly flawless flight with little, if any, wobble induced in the flight path.
Fillers, such as clay, have previously been used to reinforce nylon 11 composites see, T. D. Fornes et al., “Structure and properties of nanocomposites based on nylon 11 and 12 compared with those based on nylon 6,” Macromolecules 37, pp. 7698-7709 (2004)). The flexural modulus of the nylon 11 composite increased about 80% with a 5.7 wt. % loading of the clay. However, the impact strength decreased by 70%, which would significantly lower the performance of a shuttlecock.
In order to keep a minimum low weight of a skirt of a shuttlecock, gravity plastic materials can be used in making the skirt. For example, U.S. Pat. No. 3,904,205 teaches that polyethylene, polypropylene, EVA, ABS, and nylon can be used for making a shuttlecock skirt. However, the low gravity material addressed in this patent only satisfies the overall weight requirement in the finished shuttlecock, but fails to satisfy the impact strength requirement of the “ball” of the shuttlecock, which as previously noted is also very critical for the performance needs. Furthermore, this patent does not mention that any physical property enhancement may be obtained through cross-linking nylon 11 resin to a reinforcing filler material.
Polyamide reinforcement from inorganic filler material is disclosed in U.S. Pat. No. 3,988,287 and U.S. Published Patent Application No. 2004/0122154 A1. However, U.S. Pat. No. 3,988,287 is restricted to conventional inorganic filler materials, such as talc, clay, mica, silica, quartz, alumina, calcium carbonate, wollastonite, and carbon black; and U.S. Published Patent Application No. 2004/0122154 A1 merely teaches to exfoliate and disperse organo-clay into thermoplastic olefins (TPO) such as nylon. Both of these references fail to teach how to obtain more benefits from cross-linking conventional clay or organo-clay to a nylon resin, and also fail to teach how to overcome the brittleness of the reinforced polyamide material that is caused by the addition of the inorganic filler or organo-clay, nor do they teach or suggest that benefits can be obtained from cross-linking nylon 11 to a functionalized organo-clay material and copolymer modifiers.
U.S. Pat. No. 5,003,003 and U.S. Pat. No. 5,583,177 teach that polyamide can be blended with polyolefin elastomers such as EPDM or SEBS to have improved tensile strength, elongation, and oil resistance properties. Both patents, however, do not teach how to enhance the impact strength of polyamide material, such as using organic clay material to enhance the impact strength of the nylon 11, nor do the patents teach or suggest that useful benefits may be obtained from cross-linking the organo-clay and functionalized copolymer material, such as polyurethane into a nylon 11 resin.
Furthermore, the foregoing four references do not teach or suggest how to adjust the physical properties of a modified nylon 11 material to meet the performance requirements of a shuttlecock. For example, none of these references teach how to tailor, adjust, or customize physical properties of a nylon 11 composite such as toughness, anti-abrasion, low temperature impact resistance (e.g., at −10° C.), fatigue resistant against repeat impact, tear resistance, compression resistance, and flexural strength enhancement under high spinning. For example, U.S. Pat. No. 5,583,177 merely pertains to a polyamide resin composition used for the production of sliding parts, and has nothing to do with utilization of a nylon 11 composition improvement for a shuttlecock or equivalent application.